Method of making nonaging rimmed steel

ABSTRACT

From a heat of rimming steel, a small portion is tapped off and killed by the addition of aluminum. The remainder of the heat is teemed into ingot molds so as to fill them only partially (e.g., to 85-90 percent of the height). The partially filled molds are allowed to rim for a limited time. The molds are then filled from the aluminum-killed portion of the heat in a manner such as to cause good distribution of the added metal throughout the still molten metal in the mold. The resulting ingots are then converted to flat-rolled product by conventional methods.

United States Patent [72] lnventors Frank E. Gribble Munhnll Borough;

William G. Walk, Churchill Borough, both of, Pa. [21] Appl. No. 815,332 [22] Filed Apr. 11, 1969 [45] Patented July 20, 1971 (73] Assignee United States Steel Corporation [54] METHOD OF MAKING NONAGING RIMMED STEEL 1 Claim, 4 Drawing Figs.

[52] US. Cl 164/58 [5 l] Int. Cl ..B22d 27/18, 822d 27/20 [50] Field of Search 164/57, 58

[56] References Cited UNITED STATES PATENTS 3,414,042 12/1968 Behrens et al. 164/57 2,187,415 1/1940 Daniels 2,389,516 1 1/1945 Kinnear, .lr. 164/96 OTHER REFERENCES Production of Aluminum- Killed Steel by Mold Additions of Aluminum" by Behrens. K. F., and Hammer, R., Journal of Metals, Sept. 1967, pp. 60- 64.

Primary Examiner-4. Spencer Overhollser Assistant Examiner-V. K. Rising Anarney-Forest C. Sexton ABSTRACT: From a heat of rimming steel, a small portion is tapped off and killed by the addition of aluminum. The remainder of the heat is teemed into ingot molds so as to fill them only partially (e.g., to 85-90 percent of the height). The partially filled molds are allowed to rim for a limited time. The molds are then filled from the aluminum-killed portion of the heat in a manner such as to cause good distribution of the added metal throughout the still molten metal in the mold. The resulting ingots are then converted to flat-rolled product by conventional methods.

Law-carbon Steel and Aluminum Nan -Aging Rimmed Steel PATENTED JUL 2 0 :97:

-carb0n Low Alum Law-carbon I e e I 8 Low-carbon Steel and Aluminum Non-Aging Rimmed .Sree/ INVENTOHS. FRANK EGRIBBLE and WILLIAM G. WALK r tar/ray METHOD OF MAKING NONAGING RIMMED STEEL This invention relates to a method of making steel having the good surface quality, ductility and cleanliness characteristic of rimmed steel and also the nonaging property characteristic of steel which has been killed by aluminum additions.

BACKGROUND OF THE INVENTION Rimmed steel is preferred for drawing sheets because of its superior surface quality, ductility and cleanliness. It does, however, exhibit an aging tendency which impairs the drawing quality. Steel which has been fully killed by additions of aluminum is free from this aging tendency but is not otherwise as desirable as rimmed steel for the manufacture of drawing sheets because of its cost and lack of good surface quality. 7

It is accordingly the object of our invention to provide a method of making steel which may be converted into sheets having the good drawing property characteristic of rimmed steel and, in addition, the nonaging property characteristic of steel which has been fully killed by aluminum additions.

BRIEF SUMMARY OF THE INVENTION We provide a heat of lowcarbon steel of conventional analysis (0.03-0.12 percent C; 0.20-0.60 percent Mn and 0.04 max P) and, after tapping into a teeming ladle, draw off therefrom into a secondary ladle a small portion of theheat, say 10 percent. While filling the secondary ladle, we add aluminum to the steel entering it, to fully kill the portion of the heat thus separated from the main body of metal in the teeming ladle. We partially fill ingot molds from the teeming ladle, allow the metal in the molds to rim for a short time, then complete the filling from the secondary ladle. This effects a mixture of the aluminum killed steel with the metal in the molds which is still molten, i.e., all but the initially frozen and rimmed skin. The resulting ingots are then converted to sheets by known rolling practices.

BRIEF DESCRIPTION OF THE DRAWING A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illustrating the present preferred embodiment. In the drawings:

FIGS. 1-4 are diagrammatic representations of the several steps of our method.

DETAILED DESCRIPTION OF THE PREFERRED PRACTICE from 0.2 to 1.0 percent acid-soluble aluminum in the steel which is thus completely killed. We preferably place thermal insulating or exothermic material on top of the molten metal in ladle 12 to minimize loss of heat by radiation from the surface.

We next teem steel from ladle 110 into ingot molds 13 but fill them only partially, i.e., to a level slightly below the sideboard hot tops, if used, or to the extent of from to percent of their total height, as shown in FIG. 3. The metal in the par tially filled molds is then allowed to rim for from I to 10 minutes. After this rimming time has elapsed, we then fill molds 13 full from ladle I2, as shown in FIG. 4. During this stage, the teeming stream is preferably controlled to cause substantial penetration thereby of the central core of the ingot stillremaining molten, to effect good mixing therewith. To this end, ladle 12 preferably has a substantial ratio of height to diameter say from 2 to 4, so that a ood ferrostatic head will be available therein during the final illing of the ingot molds.

Ladle 112 may also be provided with a cover and connections for maintaining inert gas pressure therein above the liquid surface.

As an example of our method, we melted a heat of rimming steel (0.08 percent C, 0.35 percent Mn and 0.03 percent P) and tapped it into a teeming ladle 10. We then drew off 10' percent of the heat in an auxiliary ladle 112, adding aluminum sufficient to give the steel approximately 0.50 percent acidsoluble aluminum. We then filled ingot rnolds from ladle 10 to about 88 percent of their height and allowed them 5 minutes for rimming whereupon we fully filled the molds from ladle 12. This introduced sufficient aluminum into the ingot core to give about 0.06 percent acid-soluble aluminum on analysis. The ingots were then processed to flat-rolled product in the known manner.

As a result of the foregoing, the steel forming the core of the ingot will be found to contain from 0.02 to 0.09 percent aluminum. The skin of the ingot will, of course, be rimmed steel. When the ingots have been converted to slabs and rolled to sheets by conventional methods, the product will be found to have the good surface quality of the rimmed steel forming the exterior thereof and also the nonaging property characteristic of the killed steel on the interior.

Our method has important advantages in addition to producing high-quality sheet product. It is simple and inexpensive, may readily be incorporated into present ingot teeming practice and requires no special equipment and very little additional processing time.

We claim:

1. A method of making nonaging rimmed steel, the steps comprising providing a heat of rimming steel, tapping off approximately l0 to 15 percent of said heat into a ladle, adding aluminum to the tapped-off portion of the heat in sufficient quantity to deoxidize the entire heat, teeming the remainder of said heat into ingot molds, filling said molds to approximately 85 to 90 percent of capacity, then after a period of from I to [0 minutes filling the remainder of said molds with the portion of the heat to which aluminum had been added. 

